Conventionally, television broadcastings using radio transmission are carried out by ground stations. In Japan these conventional television broadcastings utilize the 1st to 12th channels in the VHF band and the 13th to 62nd channels in the UHF band, respectively. These VHF and UHF band television signals are received by VHF and UHF antennas, respectively. These VHF and UHF band television signals are then applied to VHF and UHF tuners of a conventional television receiver, respectively. These VHF and UHF tuners commonly convert the frequencies of the VHF and UHF band television signals to a predetermined intermediate frequency (referred to as IF frequency hereinafter). The television signals with the IF frequency are then applied to a video detector in the conventional television receiver.
In a cable television (referred to as CATV hereinafter) system, the frequency of a UHF band television signal is converted to a frequency in the VHF band. Then, the original VHF band television signals and the converted UHF band television signals are transmited to the VHF tuner of the conventional television receiver through a CATV line.
In a satellite television (referred to as BS television hereinafter) system, a television signal with a carrier frequency around 12 GHz in the SHF band is used. The SHF band carrier signal is frequency modulated by the BS television signal. The SHF band television signal is received by a BS antenna. The received SHF band television signal is then applied to a BS converter. The BS converter converts the frequency of the SHF band to a first IF frequency around 1.0-1.3 GHz (referred to as BS-IF frequency hereinafter). The signal with the BS-IF frequency is applied to a prescribed tuner (referred to as BS tuner hereinafter) of a conventional television receiver. The BS tuner further converts the frequency of the signal to a second IF frequency of around 130 MHz bond or 400 MHz band. Then, the signal with the second IF frequency is frequency demodulated. The FM demodulated signal is applied to the conventional television receiver.
When a user wishes to receive the respective television signals broadcasted from the ground station, the CATV station and the BS station by using a conventional television receiver, many cables must be provided for transmitting the signals from the VHF antenna, the UHF antenna, the BS antenna and a terminal coupled to a CATV main cable.
Therefore, if the user with a TV set adapted to receive television signals of the existing NTSC system utilizes each broadcasting system as described above, in addition to the cable to conduct the output of the VHF and UHF receiving antennas, cables to conduct the output of the CATV converter and BS tuner must be connected to the TV set.
Further, in a community television system, the television signals received by VHF, UHF and SHF community antennas are combined on a single transmission cable. Then the television signals are distributed to each television receiver.
Referring now to FIG. 1, such a conventional community television system adapted for receiving the VHF, UHF and the BS television signals will be briefly explained. In FIG. 1, a BS antenna 11 is provided for receiving the BS band television signal of the SHF band from a BS station. The BS band television signal is converted to the BS-IF signal by a BS converter 11a. The BS-IF signal is applied to a BS-IF cable 11b. Further a VHF antenna 12 and a UHF antenna 13 are provided for receiving the VHF and the UHF television signals from ground stations, respectively. The VHF and UHF television signals are combined by a first power combiner 14. Thus, the VHF and UHF television signals are applied to a common UV cable 14a. The BS-IF signal on the BS-IF cable 11b and the VHF and UHF television signals on the common UV cable 14a are further combined together by a second power combiner 15.
The output of the second power combiner 15 is applied to a main cable 15a. The main cable 15a is conducted to an entrance terminal 16 of a house. The entrance terminal 16 is coupled to a first separator 17 for separating the BS-IF band television signal. The other signals are applied to a second separator 18. The second separator 18 separates the VHF and the UHF band television signals. The VHF, UHF and BS-IF band television signals are the applied to a television receiver through individual tuners (not shown).
As mentioned above, conventionally, in case signals in the VHF band, UHF band and BS-IF band are received, the individual user must lead indoors a cable from the VHF receiving antenna, a cable from the UHF receiving antenna and a cable from the BS antenna, totaling three cables. In addition to this, if CATV is utilized, the connection becomes more complicated.
Moreover, if the user subscribes to a community antenna system, since the assembled signals of the signals in the VHF band, UHF band (including the CATV band) and BS-IF band are fed to the input terminal, the user must divide these into signals of each band employing a branching filter, and the connect a cable to each signal input on the television receiver, similarly to the individual user.